Fragile blanks

[nicguthrie]

Hey, I apologise if this is a subject that's been done many times or answered in depth, but I'm yet to discover the intricacies of using the forum on my phone!

I've been making pens and key fobs for friends and family recently, and have been using some gorgeous spalted and burr pieces of wood, but I've hit problems a few times and thought I'd appeal for advice from those wiser than I.

The blank has shattered several times, just as I'm finishing up and it's getting thin over the brass tube insert that it's glued to. I suspect that part of the reason was that the way I'd glued the tube in, it had not been held all the way thru, but by a few points where the CA glue had made contact before drying, so I'm trying a thick, slower drying epoxy, painted right along the length of the blank hike before inserting the tube - see if I get a more uniform attachment that way.

I was advised to try soaking blanks that are pre-known to be fragile, in watered down PVA then letting them dry before turning, but I'm worried about that changing the way finishes look.

I'm just wondering what other tricks folks may know for stopping these disappointing broken blanks, especially since some of the more rare ones can be expensive! I'm planning to get some ancient Kauri as a personal present for a friend, and don't want to lose any of those blanks - they can be up to $75 for 10.

It's also rather disheartening to lose a project just as you're finishing the final curves on it, so any advice will be greatly received!

Thanks in advance

Nic.

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[CHJ]

Just a few things that come to mind:-

Use epoxy and ensure good even coating, ensure blank hole is good fit on tube to maximise blank wall thickness and concentricity.
Soak fragile blanks with thin CA before gluing to tubes.
Keep tools as sharp as possible.
Do not generate heat when turning and finishing.

 

[Mr Finch]

A couple of other things:

I have heard mention that gorilla expanding glue or similar works better than CA as it fills in any imperfections in the drilling of the blank. Not tried this myself yet, need money to buy the glue!

Light light light touches. I have had a few explode on me and a friend said that it's because I was being too heavy with the tool.

Hope this helps!

Coll

 

[nicguthrie]

Some good tips thanks, and I'm probably guilty of both heat generation and heavy handed moments, but then I'm still pretty new to all this.

With the "soak with thin CA" would that be on the inside of the drilled hole? After all surely I'm trimming away any outside soaking as soon as I start?

I'll keep an eye open for the gorilla stuff, I have their wood glue and it seems good. I'd been put off the expanding titebond equivalent by bad reviews.

Two weeks till I get back to my workshop to try this out now - life can be cruel sometimes!

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[CHJ]

.......With the "soak with thin CA" would that be on the inside of the drilled hole? After all surely I'm trimming away any outside soaking as soon as I start?
.......

Primarily yes, but if the blank is very fragile thin CA will leach right through any cracks and voids to stiffen things up.
It's not uncommon to be advantageous to give the blank another treatment when nearing the finishing cuts.

Sometimes just applying cellulose sanding sealer as you work helps, it's a matter of past experience being your guide, and there being any need to fill little voids.

Personally I'm just lazy and unless it's something very spectacular in the way of figuring I avoid the agro. in attempting to use it anyway.

 

[nicguthrie]

Thanks very much, I'll give it a go then. The figuring on the stuff I'm using is worth the extra effort, I've got some gorgeous burr wytch elm, maple burr and some very pretty black and white spalted birch or holly can't recall which.

I never think much of anything I make but I'll post a pic of the finished article of a few of them when I get back and get them done, if anyone would like

Might try the PVA thing on the heavily spalted stuff, definitely try thin CA on the brittle wytch elm. Got to get thru two weeks holiday without getting annoyed that I can't try it now

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[Mr Finch]

Yes, would like to see some pics please.

Always interested in pen turning - a newbie myself so seeing other examples helps.

Good luck!

Coll

 

[Inspector]

As you turn down the blank re-soak it with the thin CA periodically right up to the last cuts. Put something under it to keep the drips off the bed while you apply it but not a cotton rag. Let it drink up as much as it wants each time and a light shot of accelerator will harden the excess on the outside, so that when you start the lathe again any wet ca won't spray you in the kisser. #-o Down the road if you are going to play with lots and lots of that kind of wood you may want to look at one of the wood stabilizing systems for pen turners.

Pete

 

[12345Peter]

One of the best investments you can get is a set of letter drills or similar metric equivalents. If you don't already know they are drill bits that go up in size from approx 6mm-12mm in 0.1 increments for the metric and 1/16" for imp. The size drill bit that most pen kits say to use is not necessarily the best fit, so if you use a digital calliper on the brass tube you will probably be able to select a better sized drill bit.

I liberally use CA on pen blanks even before they go near a lathe and several times while they are on the lathe if needed.

Regards
Peter

 

[CHJ]

One of the best investments you can get is a set of letter drills or similar metric equivalents. .. ......

This Drill Size Comparison Chart may be of interest.

 

[nicguthrie]

Handy! I'd actually noticed that, bought a set that specified 10mm bits but the tube had room to rattle in place when I test fitted it, so I checked with calipers and the tube wasn't much more than 9mm.

I'd started to make a chart of comparative sizes between metric and imperial, as the pen kits tend to be mixed, and I have a mix of bits. You just saved me hours CHJ tho I've also noticed that my 10mm bit is actually 9.8... so I may have a bit more measuring to go - I get a bit obsessive about accuracy, so I'd better watch out here!

Is there a cheaper, "bulk" way to buy thin CA, rather than at max 2oz bottles?

I'm also definitely looking up letter drills when I get home. Thanks guys.

Nic.

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[CHJ]

......Is there a cheaper, "bulk" way to buy thin CA, rather than at max 2oz bottles?
..

I usually buy mine from Starlock, I try to pick them up when at a model engineering show or the like to save postage.
I buy several 50grm bottles at a time and store the spares in the fridge until needed.
For hobby use there is no point in buying in larger containers as unless returned to a refrigerator between uses it will go off long before you can use it up.

Selection Chart:--- http://www.glue-shop.com/fivestar/METAL-cyano.htm

Site address:-- http://www.starloc.eu/products.htm

 

[stevenw1963]

Pound shops sell thin superglue in blister packs of 5 or 6 small bottles etc.
Ideal for soaking blanks etc & not a lot of outlay.
Keep your good stuff for tube to blank fixing.

 

[Inspector]

Is there a cheaper, "bulk" way to buy thin CA, rather than at max 2oz bottles?

We get ours from William Wood-Write here in Canada. They will be able to tell you if they can ship to you.
http://www.penblanks.ca/CA-glue-8-oz/

Pete